Recent advances in semiconductor fabrication techniques require a valve system capable of sealing between both a high pressure region and a vacuum pressure (i.e., low pressure) region. Valve systems currently used for such applications are unable to provide the reliability the semiconductor fabrication field demands. Specifically, the valves employed within conventional valve systems are unable to provide a sufficiently repeatable seal between such large pressure differentials.
Conventional valve systems employ a high pressure valve having a high pressure inlet for connecting to a high pressure gas source, and an outlet for connecting to a vacuum chamber. A "seal" is formed by moving a sealing member having a conical shaped end into a sealed position, such that the conical shaped end is forced into a conical shaped region of the outlet, typically called a seat. The metal surfaces of the sealing member's conical shaped end and the outlet's conical shaped region deform when forced against each other and thereby form a high vacuum seal. However, after a surprisingly small number of sealing cycles, the magnitude of metal-to-metal deformation required to provide a seal is no longer experienced and leakage of the high pressure gas to the low pressure side of the valve occurs. In many situations processing must cease while the high pressure valves are refurbished or replaced. Thus, when a high pressure valve is used in conjunction with a semiconductor processing chamber, where leakage through the valve will affect the vacuum level in the processing chamber, the extreme pressure differential across the conical shaped valve piece causes intolerably unreliable valve performance, and exceedingly brief valve lifetimes.
A second type of valve is available which uses a non-metallic resilient seal to "prevent" high pressure leakage. Similarly, where such vacuum type resilient seals are used, their useful life is hindered by the resilient material's tendency to extrude under high pressure, which will cause catastrophic failure of the valve if the valve is opened with high pressure on its inlet, resulting in contamination of the vacuum chamber.
Accordingly, a need exists for a valve and valve system capable of repeated effective sealing between high pressure and vacuum regions.